1 /* SPDX-License-Identifier: GPL-2.0 */
2 /*
3 * Lightweight buffered reading library.
4 *
5 * Copyright 2019 Google LLC.
6 */
7 #ifndef __API_IO__
8 #define __API_IO__
9
10 #include <errno.h>
11 #include <poll.h>
12 #include <stdlib.h>
13 #include <string.h>
14 #include <unistd.h>
15 #include <linux/types.h>
16
17 struct io {
18 /* File descriptor being read/ */
19 int fd;
20 /* Size of the read buffer. */
21 unsigned int buf_len;
22 /* Pointer to storage for buffering read. */
23 char *buf;
24 /* End of the storage. */
25 char *end;
26 /* Currently accessed data pointer. */
27 char *data;
28 /* Read timeout, 0 implies no timeout. */
29 int timeout_ms;
30 /* Set true on when the end of file on read error. */
31 bool eof;
32 };
33
io__init(struct io * io,int fd,char * buf,unsigned int buf_len)34 static inline void io__init(struct io *io, int fd,
35 char *buf, unsigned int buf_len)
36 {
37 io->fd = fd;
38 io->buf_len = buf_len;
39 io->buf = buf;
40 io->end = buf;
41 io->data = buf;
42 io->timeout_ms = 0;
43 io->eof = false;
44 }
45
46 /* Reads one character from the "io" file with similar semantics to fgetc. */
io__get_char(struct io * io)47 static inline int io__get_char(struct io *io)
48 {
49 char *ptr = io->data;
50
51 if (io->eof)
52 return -1;
53
54 if (ptr == io->end) {
55 ssize_t n;
56
57 if (io->timeout_ms != 0) {
58 struct pollfd pfds[] = {
59 {
60 .fd = io->fd,
61 .events = POLLIN,
62 },
63 };
64
65 n = poll(pfds, 1, io->timeout_ms);
66 if (n == 0)
67 errno = ETIMEDOUT;
68 if (n > 0 && !(pfds[0].revents & POLLIN)) {
69 errno = EIO;
70 n = -1;
71 }
72 if (n <= 0) {
73 io->eof = true;
74 return -1;
75 }
76 }
77 n = read(io->fd, io->buf, io->buf_len);
78
79 if (n <= 0) {
80 io->eof = true;
81 return -1;
82 }
83 ptr = &io->buf[0];
84 io->end = &io->buf[n];
85 }
86 io->data = ptr + 1;
87 return *ptr;
88 }
89
90 /* Read a hexadecimal value with no 0x prefix into the out argument hex. If the
91 * first character isn't hexadecimal returns -2, io->eof returns -1, otherwise
92 * returns the character after the hexadecimal value which may be -1 for eof.
93 * If the read value is larger than a u64 the high-order bits will be dropped.
94 */
io__get_hex(struct io * io,__u64 * hex)95 static inline int io__get_hex(struct io *io, __u64 *hex)
96 {
97 bool first_read = true;
98
99 *hex = 0;
100 while (true) {
101 int ch = io__get_char(io);
102
103 if (ch < 0)
104 return ch;
105 if (ch >= '0' && ch <= '9')
106 *hex = (*hex << 4) | (ch - '0');
107 else if (ch >= 'a' && ch <= 'f')
108 *hex = (*hex << 4) | (ch - 'a' + 10);
109 else if (ch >= 'A' && ch <= 'F')
110 *hex = (*hex << 4) | (ch - 'A' + 10);
111 else if (first_read)
112 return -2;
113 else
114 return ch;
115 first_read = false;
116 }
117 }
118
119 /* Read a positive decimal value with out argument dec. If the first character
120 * isn't a decimal returns -2, io->eof returns -1, otherwise returns the
121 * character after the decimal value which may be -1 for eof. If the read value
122 * is larger than a u64 the high-order bits will be dropped.
123 */
io__get_dec(struct io * io,__u64 * dec)124 static inline int io__get_dec(struct io *io, __u64 *dec)
125 {
126 bool first_read = true;
127
128 *dec = 0;
129 while (true) {
130 int ch = io__get_char(io);
131
132 if (ch < 0)
133 return ch;
134 if (ch >= '0' && ch <= '9')
135 *dec = (*dec * 10) + ch - '0';
136 else if (first_read)
137 return -2;
138 else
139 return ch;
140 first_read = false;
141 }
142 }
143
144 /* Read up to and including the first newline following the pattern of getline. */
io__getline(struct io * io,char ** line_out,size_t * line_len_out)145 static inline ssize_t io__getline(struct io *io, char **line_out, size_t *line_len_out)
146 {
147 char buf[128];
148 int buf_pos = 0;
149 char *line = NULL, *temp;
150 size_t line_len = 0;
151 int ch = 0;
152
153 /* TODO: reuse previously allocated memory. */
154 free(*line_out);
155 while (ch != '\n') {
156 ch = io__get_char(io);
157
158 if (ch < 0)
159 break;
160
161 if (buf_pos == sizeof(buf)) {
162 temp = realloc(line, line_len + sizeof(buf));
163 if (!temp)
164 goto err_out;
165 line = temp;
166 memcpy(&line[line_len], buf, sizeof(buf));
167 line_len += sizeof(buf);
168 buf_pos = 0;
169 }
170 buf[buf_pos++] = (char)ch;
171 }
172 temp = realloc(line, line_len + buf_pos + 1);
173 if (!temp)
174 goto err_out;
175 line = temp;
176 memcpy(&line[line_len], buf, buf_pos);
177 line[line_len + buf_pos] = '\0';
178 line_len += buf_pos;
179 *line_out = line;
180 *line_len_out = line_len;
181 return line_len;
182 err_out:
183 free(line);
184 return -ENOMEM;
185 }
186
187 #endif /* __API_IO__ */
188